The present invention relates to a data communication system. More particularly, it relates to data transfer technology suitably used in a connect-type data carrier system in which a controller device and a data carrier device are connected to each other through two lines.
FIG. 1 is a diagram for roughly showing a conventional data communication system. As shown in FIG. 1, in the conventional data communication system, a data carrier device 52 and a controller device 51 are connected to each other for data communication through four contacts respectively used for power supply, grounding, a clock and a data signal.
Since the conventional data communication system thus needs four contacts for the data communication, it is difficult to downsize the whole system.